Recently, touch panels combining display devices and position detection devices have been widely spread and used for large apparatuses such as electronic blackboards. For example, many systems for detecting positional inputs such as resistance film types, surface capacitance types, and projection capacitance types have been invented for position detection devices such as touch panels. For example, engineers have developed electronic blackboards using a plurality of color image sensors that can detect color information in addition to positional inputs so as to display colored images rendered by users (e.g. Patent Literature 1).